This invention relates to actuators. More particularly this invention relates to small hydraulic actuators.
In conventional hydraulic actuators, conventional pumps and active valves are required to guide the fluid in and out of actuator chambers in order to move actuator shafts. Typically, the pumps are heavy and require high levels of maintenance. The valves require constant manipulation, and also require substantial maintenance.
It would be desirable to provide a hydraulic actuator that is capable of substantial actuation but does not require a conventional pump.
It would also be desirable to provide a hydraulic actuator that is capable of substantial actuation but uses only passive valves, or, only a minimum of active valves.
It would also be desirable to provide a hydraulic actuator that provides the above advantages, yet allows the shaft attached to the actuator freedom of movement when power is unavailable to the actuator.
It is an object of this invention to provide a hydraulic actuator that is capable of substantial actuation but does not require a conventional pump.
It is also an object of this invention to provide a hydraulic actuator that is capable of substantial actuation but uses only passive valves, or only a minimum of active valves.
It is also an object of this invention to provide a hydraulic actuator that provides the above advantages, yet allows the shaft attached to the actuator freedom of movement when power is unavailable to the actuator.
A hydraulic actuator for actuating a shaft is provided. The actuator includes a first chamber and a second chamber adjacent to the first chamber. Fluid is passed between the chambers using a number of tubes. A divider portion of the shaft is disposed between the two chambers. The divider portion seals the first chamber from the second chamber such that when fluid flows from either chamber to the other, the shaft is actuated. The actuator also includes a plurality of deflectable membranes for causing the fluid to flow and a plurality of passive valves for directing a flow of fluid in the actuator.
A method according to the invention includes actuating a shaft using a hydraulic actuator. The method includes pre-positioning a first plurality of membranes in the actuator. Then, the method includes deflecting a second plurality of deflectable membranes in order to move fluid in the actuator such that movement of the fluid causes the shaft to move. And, when the membranes are in a non-deflectable state, allowing the shaft to respond to an external force.